Seal ring structures and methods of forming same

ABSTRACT

A three-dimensional (3D) integrated circuit (IC) includes a first IC die and a second IC die. The first IC die includes a first semiconductor substrate, and a first interconnect structure over the first semiconductor substrate. The second IC die includes a second semiconductor substrate, and a second interconnect structure that separates the second semiconductor substrate from the first interconnect structure. A seal ring structure separates the first interconnect structure from the second interconnect structure and perimetrically surrounds a gas reservoir between the first IC die and second IC die. The seal ring structure includes a sidewall gas-vent opening structure configured to allow gas to pass between the gas reservoir and an ambient environment surrounding the 3D IC.

REFERENCE TO RELATED APPLICATION

This Application claims priority to U.S. Provisional Application No.62/434,647 filed on Dec. 15, 2016, the contents of which are herebyincorporated by reference in their entirety.

BACKGROUND

The semiconductor industry has continually improved the processingcapabilities and power consumption of integrated circuits (ICs) byshrinking a minimum feature size. However, in recent years, processlimitations have made it difficult to continue shrinking the minimumfeature size for features on the ICs for successive technology nodes.The stacking of two-dimensional (2D) ICs into three-dimensional (3D) ICshas emerged as a potential approach to continue improving processingcapabilities and power consumption of ICs.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a perspective exploded view of some embodiments of athree-dimensional (3D) integrated circuit (IC) die with a seal ringstructure.

FIG. 2 illustrates a perspective view of some embodiments of the 3D ICof FIG. 1 with a first IC bonded to a second IC at a seal ringstructure.

FIG. 3 illustrates a cross-sectional view of some embodiments of FIG.2's 3D IC along the plane depicted in FIG. 2.

FIG. 4 illustrates a top view of some embodiments of a first IC die,which includes a first seal ring segment circumscribing contact pads orcontact plugs, in accordance with some embodiments of FIG. 3.

FIG. 5 illustrates a top view of some embodiments of a portion of a sealring structure corresponding to the inset area shown in FIG. 4.

FIG. 6 illustrates a cross-sectional view of some embodiments of a 3D ICincluding a first IC bonded to a second IC at a seal ring structure,along a cross-sectional plane as indicated on FIG. 4.

FIG. 7 illustrates a cross-sectional view of some embodiments of aportion of a seal ring structure corresponding to the inset area shownin FIG. 6.

FIGS. 8, 9, 10, 11, 12, and 13A-13C illustrate a series of perspectiveviews of some embodiments of a method for manufacturing a 3D IC die witha seal ring structure.

FIGS. 14, 15, and 16A-16B illustrate perspective views of some otherembodiments that may be utilized in the methods depicted in FIGS. 8though 13A-13C.

FIG. 17 illustrates a perspective view of some other embodiments of afirst or second IC die that includes a seal ring segment.

FIG. 18 illustrates a perspective view of some other embodiments of afirst or second IC die that includes a seal ring segment.

FIG. 19 illustrates a manufacturing method as a flow chart in accordancewith some embodiments.

DETAILED DESCRIPTION

The present disclosure provides many different embodiments, or examples,for implementing different features of this disclosure. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper”, and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice or apparatus in use or operation in addition to the orientationdepicted in the figures. The device or apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly. Even more, the terms “first”, “second”, “third”, “fourth”,and the like are merely generic identifiers and, as such, may beinterchanged in various embodiments. For example, while an element(e.g., conductive wire) may be referred to as a “first” element in someembodiments, the element may be referred to as a “second” element inother embodiments.

One type of three-dimensional (3D) integrated circuit (IC) comprises afirst IC die and a second IC die stacked over the first IC die. Thefirst IC die includes a first semiconductor substrate and a firstinterconnect structure; while the second IC die includes a secondsemiconductor substrate and a second interconnect structure. The firstand second interconnect structures each comprise alternating stacks ofwiring layers and via layers. Contact pads or plugs are disposed onupper surfaces of the first and second interconnect structures. Thecontact pads or plugs of the first IC die are in direct contact with thecontact pads or plugs of the second IC die to bond the first and secondIC dies to one another.

A seal ring structure, which is sandwiched between the first and secondIC dies, perimetrically encloses the contact pads or plugs of the firstand second IC dies, and protects the 3D IC. For example, the seal ringstructure may protect the 3D IC from a die saw, and/or moisture and/orgases diffusing into (or out of) the 3D IC die. In some technologies,the seal ring structure is formed when a first seal ring segment, whichis disposed on a face of the first IC die, is bonded to a second sealring segment, which is disposed on a face of the second IC die. An outersurface of each seal ring segment is continuously planar over its entireextent, and is co-planar with the contact pads or plugs of that IC die.Thus, when the first and second seal ring segments are pressed togetherto bond the first IC to the second IC, the seal ring segmentscollectively form the seal ring structure to protect the contact pads orplugs. Because each seal ring segment has an outer surface that iscontinuously planar, this configuration helps ensure maximum surfacearea for bonding between the seal ring segments, and helps ensure goodelectrical connection between the contact pads or plugs on adjacentfaces of the first and second die. However, some aspects of the presentdisclosure contemplate that fully co-planar seal rings and contact padsor plugs can actually be detrimental in that, during manufacturing whenthe first and second ICs are pressed together, gas can be trapped withinan inner cavity that is bounded by the seal ring and confined betweenthe faces and of first and second ICs. As the first and second ICs arepressed together for hybrid bonding, the trapped gas can cause the firstand second ICs to be pushed away from one another, leading toreliability concerns, particularly in the wake of temperature changeswhich can alter the pressure asserted by the trapped gas.

In view of the foregoing, various embodiments of the present applicationare directed towards techniques that utilize a seal ring with a sidewallgas-venting structure. This sidewall gas-venting structure includesopenings that allow gas to escape from within the confines of the sealring between the first and second IC dies, but the structure stillpromotes strong hybrid bonding between the first and second IC dies. Thestructure may also be beneficial in that the openings can also limitpropagation of pressure waves that can arise during bonding, and canthereby help improve bonding effectiveness.

With reference to FIGS. 1-5, some embodiments of a 3D IC 100 with a sealring structure is provided. As illustrated in FIG. 1's perspectiveexploded view, the 3D IC 100 includes a first IC die 102 a includingfirst seal ring segment 104 a that perimetrically circumscribes one ormore first contact plugs or contact pads (e.g., 106 a), and a second ICdie 102 b including a second seal ring segment 104 b that perimetricallycircumscribes one or more second contact plugs or contact pads (e.g.,106 b). The first and second seal ring segments 104 a, 104 b havenearest faces (e.g., 108 a, 108 b, respectively), which are planar orsubstantially planar, and which are co-planar or substantially co-planarwith nearest faces of the first and second contact plugs or contact pads(110 a, 110 b, respectively). Notably, the first seal ring segment 104 acan extend outward beyond a face 112 a of the first IC die 102 a, suchthat a first recess is defined along face 112 a within seal ring segment104 a; while the second seal ring segment 104 b can extend outwardbeyond a face 112 b of the second IC die 102 b, such that a secondrecess is defined along face 112 b within seal ring segment 104 b. Dueto this geometry, the first and second recesses can serve as a gasreservoir 116 (see FIG. 3) when the first seal ring segment 104 a isbonded to the second seal ring segment 104 b.

As shown in FIG. 2, when the first IC die 102 a and second IC die 102 bare bonded together, for example at a hybrid bond interface, the nearestfaces (which may also be referred to as first and second bonding surfaceregions 108 a, 108 b, respectively) of the first and second seal ringsegments (104 a, 104 b) are in direct contact with one another, andnearest faces (e.g., 110 a, 110 b in FIG. 1) of the first and secondcontact plugs are in direct contact with one another. The first andsecond bonding surface regions 108 a, 108 b of the first and second sealring segments 104 a, 104 b are configured to directly contact oneanother, so as to provide a sufficient contact area that yields a hybridbond of sufficient strength to bond the first IC die 102 a to the secondIC die 102 b. The first and second contact pads or plugs 106 a, 106 bare also in direct contact, thereby electrically coupling the firstcontact pads or plugs to the second contact pads or plugs. The first andsecond seal ring segments 104 a, 104 b, prior to bonding or afterbonding, may also be referred to individually and/or collectively as aseal ring structure 104.

The seal ring structure 104 extends from one IC die (e.g., the first ICdie 102 a) to another IC die (e.g., the second IC die 102 b), such thatthe seal ring structure 102 defines a wall or barrier protecting the 3DIC. For example, the seal ring structure 104 may protect the 3D IC froma die saw singulating the first and second IC dies 102 a, 102 b and/orfrom gases diffusing into (or diffusing out of) the first and second ICdies 102 a, 102 b from (or into) an ambient environment of the first andsecond IC dies 102 a, 102 b. Further, although FIG. 1 illustrates theseal ring structure 104 is made up of a single ring-shaped structure, inother embodiments the seal ring structure can include multiple ringsthat are concentrically aligned.

In some embodiments, the first contact plugs or contact pads 106 a andthe first seal ring segment 104 a are made of the same material or havethe same composition. In other embodiments, the first seal ring segmentis distinct from, and/or a different material than, the first contactplugs or contact pads. For example, in some embodiments, the first sealring segment and first contact plugs or contact pads are made of pureelemental copper or are made of a copper alloy. Similarly, in someembodiments, the second seal ring segment 104 b is integrated with,and/or the same material as, the second contact plugs or contact pads106 b. In other embodiments, the second seal ring segment is distinctfrom, and/or a different material than, the second contact plugs orcontact pads. The second seal ring segment can be made of the samematerial as the first seal ring segment in typical embodiments, but canalso be made of different material and/or have different compositions inother embodiments.

Notably, the bonding surface for at least one of the first and/or secondseal ring segments 104 a, 104 b is broken or punctured by one or moresidewall openings 114, which establish a sidewall gas-venting structurethat allows gas to escape from the gas reservoir 116 (see e.g., gas flowarrows 200 in FIG. 2). In this way, the surfaces of the first and secondseal ring segments, which can include uppermost planar portions (e.g.,108 a) and recessed portions (e.g., 116), are structured to allow forgas ingress and egress to mitigate pressure buildup and to facilitatemore reliable hybrid bonding at the hybrid bond interface.

In some cases, only a single sidewall recess is present within only oneof the first and second seal ring segments 104 a, 104 b, which isadvantageous in that it provides a very large surface bonding area onthe seal ring segments, while in other cases, such as illustrated inFIGS. 1-5, many sidewall recesses are present, which is advantageous inthat it tends to allow better gas flow for ingress/egress. In someembodiments where multiple sidewall recesses are present, the sidewallopening 114 can be distributed at regular intervals and can have equalsizes as one another, while in these and other embodiments the sidewallopening 114 can be randomly distributed and/or have different sizes fromone another.

FIG. 3 shows a cross-sectional view of the 3D IC 100 of FIG. 2, asindicated by the cross-sectional plane depicted in FIG. 2. As can beseen in FIG. 3, the first IC die 102 a includes a first semiconductorsubstrate 300 a while the second IC die 102 b includes a secondsemiconductor substrate 300 b. In some embodiments, the semiconductorsubstrates 300 a, 300 b are bulk substrates of monocrystalline siliconor some other semiconductor, or are semiconductor-on-insulator (SOI)substrates, or other substrates, or a combination of the foregoing.Further, in some embodiments, the semiconductor substrates 300 a, 300 bhave respective thicknesses that are the same or different. For example,the first semiconductor substrate 300 a of the first IC die 102 a mayhave a first thickness and the second semiconductor substrate 300 b ofthe second IC die 102 b may have a second thickness that is equal to orgreater than the first thickness.

The first and second IC dies 102 a, 102 b also include first and secondinterconnect structures 302 a, 302 b respectively, which separate thesemiconductor substrates 300 a, 300 b from one another. A firstinterconnect structure 302 a comprises an interlayer dielectric (ILD)layer 304 a, a first wiring layer 306 a, and a first via layer 308 a.Similarly, a second interconnect structure 302 b comprises an interlayerdielectric (ILD) layer 304 b, a first wiring layer 306 b, and a firstvia layer 308 b. Other wiring layers, via layers, and/or contact layerscan also be present, and any number of such layers may be presentdepending on the technology involved. The ILD layers may be, forexample, silicon dioxide, a low κ dielectric, some other dielectric, ora combination of the foregoing. As used here, a low κ dielectric is adielectric with a dielectric constant κ less than about 3.9. The wiringlayers, the via layers, and contact layers are conductive and may be,for example, aluminum copper, copper, aluminum, tungsten, some othermetal or conductive material, or a combination of the foregoing. In someembodiments, the seal ring structure 104 is isolated from the metallayers and vias of the first and second interconnect structures.

A plurality of semiconductor devices, such as transistor device 310, areelectrically coupled to one another through the first and/or secondinterconnect structures 302 a, 302 b. In some embodiments, thesemiconductor devices are active and/or passive devices, and/or are inthe semiconductor substrates 300 a, 300 b of FIG. 3 and/or theinterconnect structures 302 a, 302 b of FIG. 3. For example, thesemiconductor devices may comprise insulated-gate field-effecttransistors (IGFETs) or metal-oxide-semiconductor field-effecttransistors (MOSFETs), bipolar junction transistors (BJTs), fin fieldeffect transistors (FinFETs), diodes, and/or other devices, arranged inthe semiconductor substrates of FIG. 3. As another example, thesemiconductor devices may comprise metal-insulator-metal (MIM)capacitors, resistive random-access memory (RRAM), or spiral inductorsarranged in the interconnect structures 302 a, 302 b of FIG. 3.

As shown in FIG. 4, in some embodiments the first seal ring segment 104a includes a series of cube-like or box-like structures 402, 404. Afirst cube-like or box-like structure 402 is relatively wide andrelatively tall, while a second cube-like or box-like structure 404 isrelatively narrow and relatively short in comparison. Consecutivecube-like or box-like structures can have squared off corners as shownin FIG. 4, or can have rounded or tapered corners, as shown in FIG. 5.In FIG. 5, consecutive cube-like or box-like structures 402, 404 areshown to alternate between a first width, w₁, and a second width, w₂,which is greater than the first width. Further, in some embodiments, thecube-like or box-like structures 402 have a first length, L₁ and theshorter cube-like or box-like structures have a second length, L₂, whichcan be equal to the first length as shown in FIG. 5. In otherembodiments, the second length can differ from the first length—forexample the second length can be less than or greater than the firstlength. The first length and second length can each range fromapproximately 0.6 μm to approximately 4 μm, and can each beapproximately 0.6 μm in some embodiments. The first width and secondwidth can each range from approximately 0.8 μm to approximately 8 μm,and can each be approximately 1 μm in some embodiments.

As shown in FIG. 6, consecutive cube-like or box-like structuresalternate between taller cube-like or box-like structures 402 andshorter cube-like or box-like structures 404. The taller cube-like orbox-like structures 402 can have a first height, h₁, and the shortercube-like or box-like structures 404 can have a second height, h₂,wherein the heights can be measured vertically from the face of thefirst IC die and/or second IC die. Thus, the taller cube-like orbox-like structures 402, which are at the first height, have uppermostsurfaces 402 a, 402 b that are coplanar with one another, and theshorter cube-like or box-like structures 404 have uppermost surfaces 404a, 404 b that are recessed relative to the uppermost surfaces of thetaller cube-like or box-like structures 402. Although not shown in FIG.6-7, the first contact pads or contact plugs 106 a (see FIG. 3) have athird height, which is equal to the first height, and which is greaterthan the second height. In this way, when the first IC die 102 a isbonded to the second IC die 102 b, the first and second contact pads orcontact plugs 106 a, 106 b have faces that directly contact one anotherso as to be planarly flush with one another. Taller cube-like orbox-like structures (e.g., 402 in FIGS. 4-7) are also planarly flushwith one another, while shorter cube-like or box-like structures (e.g.,404 in FIGS. 4-7) give rise to a sidewall opening 114 that allows gas toescape from the gas reservoir 116 circumscribed by the first and secondseal ring segments 104 a, 104 b. For example, a height ratio of h₂/h₁can range from zero to 0.999 in some embodiments, and can range from0.25 to 0.75 in other embodiments, and can be approximately 0.50 instill other embodiments.

In some embodiments, such as shown in FIG. 7, the uppermost surfaces ofthe shorter cube-like or box-like structures 404 are rounded or taperedand are recessed relative to the uppermost surfaces 402 a, 402 b,respectively of the taller cube-like or box-like structures 402. In someof these embodiments, the rounded or tapered uppermost surfaces 404 a,404 b can exhibit CMP scratches or abrasions, which arise from CMP“dishing” of the shorter cube-like or box-like structures 404 duringmanufacture.

Because the uppermost surfaces of the taller cube-like or box-likestructures are in direct contact with one another and can be wider thanthe shorter cube-like or box-like structures in some embodiments, asurface contact area between the first and second seal ring segments canbe greater than 50% in some embodiments. For example, in someembodiments, the surface area of the uppermost surface of each tallercube-like or box-like structure can be approximately 1 μm², while thesurface area of the uppermost surface of each shorter cube-like orbox-like structure can be approximately 0.36 μm². Thus, the ratio of thesurface area of the uppermost surface of each taller cube-like orbox-like structure to the surface area of the uppermost surface of eachshorter cube-like or box-like structure can be approximately 36% in somecases, but can more generally range between 5% and 95%, depending on theimplementation. In these and other embodiments, the contact surface areabetween the first and second seal ring segments can range between 1% and99%, or between 20% and 70% in other embodiments, and beingapproximately between 25% and 50% in still other embodiments.

While FIGS. 1-4 and 6 show the sidewalls of the cube-like or box-likestructures as being planar, it other embodiments the sidewalls can havea rounded surface geometry, tapered surface geometry, spherical orsphere-like surface geometry, undulating surface geometry, saddle-likegeometry, or other non-planar surface geometry—see e.g., FIG. 5 and FIG.7. Vertical sidewalls or substantially vertical sidewalls, asillustrated, are advantageous however, in that they provide a relativelycompact footprint from the seal ring while will providing a relativelylarge amount of planar surface area for bonding at the interface to theother IC die. On the other hand, due to dishing of small areas, roundedor tapered surfaces may evidence the use of CMP in forming gas-ventingstructures, which may save one or more masks steps and are perhaps evenmore advantageous.

With reference to FIGS. 8-13, a series of perspective views illustratesome embodiments for a method of manufacturing a 3D IC die with a sealring structure. While the methods herein are illustrated and describedherein as a series of acts or events, it will be appreciated that theillustrated ordering of such acts or events are not to be interpreted ina limiting sense. For example, some acts may occur in different ordersand/or concurrently with other acts or events apart from thoseillustrated and/or described herein. Further, not all illustrated actsmay be required to implement one or more aspects or embodiments of thedescription herein, and one or more of the acts depicted herein may becarried out in one or more separate acts and/or phases.

In FIG. 8, a first IC die precursor 102 a′ is formed, and a conductivebond ring and pad layer 802 is formed over an upper surface of the firstIC die precursor. For example, in some embodiments, the conductive bondring and pad layer 802 is made of copper, copper alloy, aluminum, oranother metal, and is formed by electroplating or by sputtering. In someembodiments, the first IC die precursor 102 a′ can include a substrateand interconnect structure, such as illustrated and described withregards to FIG. 3 for example.

In FIG. 9, a first mask (not shown) is formed over an upper surface ofthe conductive bond ring and pad layer 802 using lithography techniques.A first etch, such as a wet etch, dry etch, plasma etch, or other etch,is carried out with the first mask in place to form one or moreconductive pads or plugs 106 a′ extending upward from a face of thefirst IC die precursor 102 a′, and to form a bond-ring precursor 104 a′circumscribing the one or more conductive pads or plugs 106 a′. The bondring precursor 104 a′ has a substantially planar upper surface, whichextends in continuous planar fashion around the entirety of the bondring precursor 104 a′. The substantially planar upper surface may havesome hillocks or valleys which were present in the initial conductivebond ring and pad layer 802, which could arise due to randomfluctuations in the deposition or sputtering process. As viewed fromabove, the bond ring precursor 104 a′ has at least one narrow portion902 which will correspond to a sidewall vent region in the bond ringprecursor. In the illustrated embodiment, a series of narrow portions902 having equal widths and lengths are distributed at regular intervalsover the perimeter of the bond ring precursor 104 a′. The narrowportions 902 are spaced apart from one another by wide portions 904 ofthe bond ring precursor. Depending on the characteristics of the firstetch, the sidewalls of the wide portions 904 may have tapered sidewallsor vertical sidewalls. In some cases, the first etch may result in thewide portions 904 being cube-like, box-like, cylindrical, pyramid,frustum pyramid in shape, or frustum cone in shape, or if the etchundercuts the mask, being inverted frustum pyramid in shape or invertedfrustum cone in shape. Narrow portions 902 can also be cube-like,box-like, cylindrical, pyramid, frustum pyramid in shape, frustum conein shape, inverted frustum pyramid in shape or inverted frustum cone inshape. In combination, the narrow portions 902 and wide portions 904perimetrically surround an area on a face of the first IC die precursor102 a′.

In FIG. 10, a chemical mechanical planarization (CMP) operation iscarried out to fashion a seal ring segment 104 a. The seal ring segment104 a has wide portions 904 with upper planar surfaces which areco-planar with one another, thereby providing a good bonding surface.Due to the narrow portions 902 having less structural integrity than thewide portions 904, upper surfaces of the narrow portions may experience“dishing” (see 906) and may thereby become recessed relative to uppersurfaces of the wide portions. Thus, sidewall recesses for venting ofgas, which correspond to a concave upper surface of the narrow portions902, can be formed in the seal ring segment 104 a in this manner. Uppercorners of the wide regions may also become rounded due to the CMP,while central portions of the wide regions tend to become wellplanarized with upper surfaces of the conductive pads or plugs. Theuppermost surfaces of the narrow regions can be rounded or tapered, andcan include CMP abrasions or scratches arising from the CMP processused.

In some embodiments, rather than using CMP to form the recesses in thenarrow portions 902 of the seal ring segment 104 a, the recesses couldalso be formed by patterning a second mask over the wide portions 904 ofthe seal ring segment 104 a, and then carrying out an etch with thesecond mask in place. Depending on the etch characteristics, thesidewalls of the wide portions may have tapered sidewalls or verticalsidewalls. In some cases, the second etch may result in the wideportions being frustum pyramid in shape or frustum cone in shape, or ifthe etch undercuts the mask, being inverted frustum pyramid in shape orinverted frustum cone in shape. It will be appreciated, however, thatforming the concave recesses in the narrow portions 902 of the seal ringsegment 104 a through CMP is particularly advantageous in that it savesthe capital expense of a mask as well as the processing time and costsassociated with the photolithography and subsequent etching. Therefore,the narrow portions 902 of the seal ring segment 104 a having a roundedor tapered upper surface that extends in a circular, parabolic, or othercontinuous curve between planar upper surfaces of neighboring wideportions is an advantageous configuration.

In FIG. 11, the first IC die 102 a is place in close proximity to asecond IC die 102 b. The second IC die 102 b can correspond to thesecond IC die 102 b previously described in FIGS. 1-5, for example,and/or can have structural features corresponding to the first IC die104 a, albeit most likely with devices arranged in a different circuitconfiguration on the first and second IC die. Thus, in some embodiments,the second IC die 104 b includes a second bond ring segment 104 b thatis congruous and/or geometrically similar to the first bond ring segment104 a.

In FIG. 12, the first IC die 102 a is bonded to the second IC die 102 b,for example through a direct bonding process, a fusion bonding process,or a hybrid bonding process, for example. The first IC die 102 a andsecond IC die 102 b are bonded together at a bond interface, such thatthe nearest faces (e.g., 108 a, 108 b in FIG. 1) of the first and secondseal ring segments are in direct contact with one another, and nearestfaces (e.g., 110 a, 110 b in FIG. 1) of the first and second contactplugs are in direct contact with one another. The first and secondplanar surfaces of the seal ring segments are configured to directlycontact one another to form a seal ring, so as to provide a sufficientcontact area that yields a hybrid bond of sufficient strength toreliably bond the first IC die 102 a to the second IC die 102 b. Thefirst and second contact pads or plugs are also in direct contact,thereby electrically coupling the first contact pads or plugs to thesecond contact pads or plugs. The seal ring perimetrically surrounds agas reservoir which is in fluid communication with the ambientenvironment solely through the sidewall recesses, which establishsidewall vent openings.

In FIG. 13A-13C, additional process steps are carried out to formmaterial 1310 that blocks or “pinches off” the sidewall vent openingsafter bonding is complete. In FIG. 13A, an anneal or other heattreatment is carried out to at least partially liquefy the first andsecond seal ring segments 104 a, 104 b to close or “pinch off” thesidewall vent openings. The heat treatment also causes the first andsecond seal ring segments 104 a, 104 b, which were previously distinctcrystal structures, to form crystalline grains that grow across theprevious planar interface at which the first and second seal ringsegments met. Thus, this heat treatment, which can take the form of ananneal for example, can partially melt the first and/or second seal ringsegments to coalesce into a single continuous body of conductivematerial. This helps to ensure the seal ring provides good protectionfrom the ambient environment after manufacturing is complete. In FIG.13A, the anneal or other heat treatment is carried out in a manner thatthe seal ring outer sidewalls are a substantially continuous planarsurface along their outer perimeter.

In FIG. 13B, the additional process steps, which could take the form ofa heat treatment or deposition, are carried out such that the seal ringouter sidewalls include ridges. The narrow portion of the ridges includematerial 1310 that blocks the sidewall vent openings. Thus, thestructure includes wide ridges corresponding to wide portions 904 andnarrow ridges which correspond to narrow portions 902.

In FIG. 13C, material 1310 takes the form of a protective layer, such asa nitride, oxide, epoxy, or ceramic among others, that has been formedover the outer sidewalls of the seal ring structure to cover, fill,and/or plug the sidewall vent openings, thereby helping ensure goodprotection from the ambient environment after manufacturing is complete.In some embodiments, the protective layer can be made of a differentmaterial and/or can have a different lattice structure (e.g., adifferent crystalline lattice structure) than the other portions of thefirst and second seal ring segments 104 a, 104 b.

While FIGS. 11-13 show a manufacturing example where the first andsecond IC dies each include a seal ring that include one or moresidewall vent openings, in other embodiments, one of the first andsecond IC dies can include a fully planar upper surface for its sealring segment and the other of the first and second IC dies can includeone or more sidewall vent openings. FIGS. 14-15 illustrate one suchexample. In FIG. 14, the first IC die 1402 a includes a first seal ringsegment 1404 a having a series of large box-like or cube-like structureshaving a first width and first height, and which alternate with smallbox-like or cube-like structures having a second width and secondheight. The first width is larger than the second width, and the firstheight is larger than the second height, which gives rise to sidewallvent openings in the first IC die 1402 a. The second IC die 1402 bincludes a second seal ring segment 1404 b having a planar upper surfacethat extends continuously around an entire upper surface of the secondseal ring segment 1404 b. In FIG. 15, the first IC die 1402 a is bondedto the second IC die 1402 b, for example through a direct bondingprocess, a fusion bonding process, or a hybrid bonding process, forexample. In FIGS. 16A-16B, additional process steps are carried out toblock or “pinch off” the sidewall vent openings after bonding iscomplete.

FIGS. 17 and 18 illustrate some additional embodiments in which a firstand/or second seal ring segment includes a plurality of ring-shapedsegments that are concentrically aligned about a central axis which isperpendicular to a face of the IC die. In FIG. 17, a seal ring segment1702 includes a series of relatively wide and relatively tall cube-likeor box-like structures 1704, which are separated from one another byrelatively narrow cube-like or box-like structures 1706. In this case,the relatively narrow cube-like or box-like structures are arranged intwo concentric rings—an inner ring 1706 a, and outer ring 1706 b. Uppersurfaces of the two concentric rings 106 are recessed relative to theupper surfaces of the relatively wide and relatively tall cube-like orbox-like structures 1704, such that upper surfaces of the relativelynarrow cube-like or box-like structures 1706 correspond to gas ventopenings. The structure of FIG. 17 can again be formed by usinglithography to pattern a bond ring precursor, which has a substantiallyplanar upper surface around the entire bond ring precursor and acombination of relatively wide and relatively narrow features, and thenperforming CMP on the bond ring precursor to planarize the upper surfaceof the relatively wide features 1704 and to recess the relatively narrowfeatures 1706 to efficiently form the gas vent openings.

In FIG. 18, a seal ring segment 1802 includes a series of relativelywide and relatively tall cube-like or box-like structures 1804, whichare separated from one another by relatively narrow cube-like orbox-like structures 1806. The narrow cube-like or box-like structures1806 include multiple rails 1806 a, 1806 b, 1806 c, 1806 d that arestacked over one another to give rise to the gas vent openings. Thisstructure can be formed using multiple lithography and etching steps,and while falling within the scope of the present disclosure, is lessefficient from a processing perspective than some other embodimentswhere CMP is used to form the sidewall gas vent openings.

FIG. 19 illustrates a method in accordance with some embodiments. At1902, a first seal ring segment is formed over a first face of a firstIC die. The first seal ring segment perimetrically encloses a first areaon the first face of the first IC die and includes a first bondingsurface region. In some embodiments, 1902 can correspond to FIG. 9 orFIG. 10.

At 1904, a second seal ring segment is formed over a second face of asecond IC die. The second seal ring segment perimetrically encloses asecond area on the second face of the second IC die and includes asecond bonding surface region. In some embodiments, 1904 can correspondto forming 102 b in FIG. 11. At least one of the first seal ring segmentand the second seal ring segment, if not both, includes a sidewallgas-venting opening.

At 1906, the first IC die is bonded to the second IC die so the firstbonding surface region contacts the second bonding surface region. Thus,a seal ring structure that encloses a gas reservoir between the firstface and the second face is established. The sidewall gas-ventingopening is configured to allow gas to pass between the gas reservoir andan ambient environment surrounding the 3D IC. In some embodiments, 1906can correspond to FIG. 11 or FIG. 14.

At 1908, the gas reservoir is hermetically sealed from the ambientenvironment. In the illustrated embodiment, this can be achieved by (a)performing a heat treatment to soften or liquefy material of the firstseal ring segment or the second seal ring segment, thereby pinching offthe opening, or by (b) forming a coating or plug to block the openingand hermetically seal the gas reservoir from the ambient environment. Insome embodiments, 1908 can correspond to FIGS. 13A-13C or FIGS. 16A-16B.

In view of the foregoing, some embodiments of the present applicationprovide a method for manufacturing a three-dimensional (3D) integratedcircuit (IC). In the method, a first seal ring segment is formed over afirst face of a first IC die. The first seal ring segment perimetricallyencloses a first area on the first face of the first IC die and includesa first bonding surface region. A second seal ring segment is formedover a second face of a second IC die. The second seal ring segmentperimetrically encloses a second area on the second face of the secondIC die and includes a second bonding surface region. At least one of thefirst seal ring segment and the second seal ring segment includes asidewall gas-venting structure. The first IC die is bonded to the secondIC die so the first bonding surface region contacts the second bondingsurface region, thereby establishing a seal ring structure that enclosesa gas reservoir between the first face and the second face. The sidewallgas-venting structure is configured to allow gas to pass between the gasreservoir and an ambient environment surrounding the 3D IC.

Other embodiments relate to a method for manufacturing athree-dimensional (3D) integrated circuit (IC). In the method, a firstIC die precursor is formed with a first seal ring precursor extendingoutward from a face of the first IC die precursor. One or moreconductive contact areas or plugs is circumscribed by the first sealring precursor, and the seal ring precursor includes a bonding surfaceregion including a first region having a first width and a second regionhaving a second width less than the first width. A chemical mechanicalplanarization (CMP) process is performed on the first seal ringprecursor and the one or more conductive contact areas or plugs, therebyforming a first IC die having a first seal ring segment. The CMP processmakes upper surfaces of the one or more conductive contact areas orplugs co-planar with the first region of the bonding surface region andconcurrently recesses upper surfaces of the second region for the firstIC die. The first IC die is bonded to a second IC die so upper surfacesof the one or more conductive contact areas or plugs of the first IC diedirectly contact one or more corresponding conductive contact areas orplugs of the second IC die and so the upper surface of the first regionsof the first seal ring segment directly contacts a second seal ringsegment of the second IC die. The recessed upper surfaces of the secondregion provide gas vent openings to a gas reservoir between the first ICdie and the second IC die.

Other embodiments relate to a method for manufacturing athree-dimensional (3D) integrated circuit (IC). In the method, a firstseal ring segment is formed over a first face of a first IC die. Thefirst seal ring segment circumscribes a first contact area or plug onthe first face. A second seal ring segment is formed over a second faceof a second IC die. The second seal ring segment circumscribes a secondcontact area or plug on the second face. At least one of the first sealring segment and the second seal ring segment includes a sidewallgas-venting structure. The first seal ring segment is bonded to thesecond seal ring segment so the first contact area or plug contacts thesecond contact area or plug, thereby establishing a seal ring structurethat encloses a gas reservoir between the first face and the second facesuch that the sidewall gas-venting structure facilitates gas flowbetween the gas reservoir and an ambient environment surrounding the 3DIC. The sidewall gas-venting structure is then pinched off either byperforming a heat treatment to soften or liquefy material of the firstor second seal ring segment or by depositing a coating on an outersidewall of the seal ring structure.

Still other embodiments relate to a three-dimensional (3D) integratedcircuit (IC). The 3D IC includes a first IC die and a second IC die. Thefirst IC die includes a first semiconductor substrate, and a firstinterconnect structure over the first semiconductor substrate; and thesecond IC die includes a second semiconductor substrate, and a secondinterconnect structure that separates the second semiconductor substratefrom the first interconnect structure. A seal ring structure separatesthe first interconnect structure from the second interconnect structureand perimetrically surrounds a gas reservoir between the first IC dieand second IC die. The seal ring structure includes a sidewall gas-ventopening structure configured to allow gas to pass between the gasreservoir and an ambient environment surrounding the 3D IC.

Further embodiments relate to a three-dimensional (3D) integratedcircuit (IC) including a first IC die and a second IC die. The first ICdie includes a first semiconductor substrate, and a first interconnectstructure, which includes a first contact pad, over the firstsemiconductor substrate. The second IC die includes a secondsemiconductor substrate and a second interconnect structure. The secondinterconnect structure separates the first interconnect structure fromthe second substrate and has a second contact pad in direct contact withthe first contact pad. A seal ring, which includes a sidewall ventopening structure, perimetrically surrounds the first and second contactpads and perimetrically surrounds a gas reservoir between the first ICdie and second IC die. A material is disposed in the sidewall ventopening structure and is configured to hermetically seal the gasreservoir from an ambient environment surrounding the 3D IC.

Other embodiments relate to a three-dimensional (3D) integrated circuit(IC) that includes a first IC die and a second IC die. The first IC dieincludes a first semiconductor substrate, a first interconnect structureover the first semiconductor substrate, and a first seal ring segmentover the first interconnect structure. The first seal ring segmentperimetrically surrounds an area of the first interconnect structure.The second IC die includes a second semiconductor substrate, a secondinterconnect structure, and a second seal ring segment. The secondinterconnect structure separates the first interconnect structure fromthe second substrate, and the second seal ring segment perimetricallysurrounds an area of the second interconnect structure. The first sealring segment has a first bonding surface that is in direct contact witha second bonding surface of the second seal ring segment, except for ata sidewall vent opening structure which penetrates entirely through atleast one of the first seal ring segment or the second seal ringsegment.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

1. A method for manufacturing a three-dimensional (3D) integratedcircuit (IC), the method comprising: forming a first seal ring segmentover a first face of a first IC die, wherein the first seal ring segmentperimetrically encloses a first area on the first face of the first ICdie and includes a first bonding surface region; forming a second sealring segment over a second face of a second IC die, wherein the secondseal ring segment perimetrically encloses a second area on the secondface of the second IC die and includes a second bonding surface region,wherein at least one of the first seal ring segment and the second sealring segment includes a sidewall gas-venting structure; and bonding thefirst IC die to the second IC die so the first bonding surface regioncontacts the second bonding surface region, thereby establishing a sealring structure that encloses a gas reservoir between the first face andthe second face, wherein the sidewall gas-venting structure isconfigured to allow gas to pass between the gas reservoir and an ambientenvironment surrounding the 3D IC.
 2. The method of claim 1, wherein thesidewall gas-venting structure comprises an opening that fullypenetrates through at least one sidewall of the at least one of thefirst seal ring segment and the second seal ring segment.
 3. The methodof claim 2, further comprising: performing a heat treatment to soften orliquefy material of the first seal ring segment or the second seal ringsegment to pinch off the opening and hermetically seal the gas reservoirfrom the ambient environment.
 4. The method of claim 2, furthercomprising: forming a coating or plug to block the opening andhermetically seal the gas reservoir from the ambient environment.
 5. Themethod of claim 1, wherein the first seal ring segment comprises aseries of cube-like or box-like structures having different heights anddifferent widths which perimetrically enclose the first area, andwherein a difference in the heights and/or widths gives rise to thesidewall gas-venting structure.
 6. The method of claim 5, furthercomprising: prior to bonding the first seal ring segment to the secondseal ring segment, performing a chemical mechanical polishing (CMP)process on the first bonding surface region of the first seal ringsegment; and wherein the CMP process reduces the heights of cube-like orbox-like structures having smaller widths faster than the CMP processreduces the heights of cube-like or box-like structures having largerwidths, thereby forming a recess in the first bonding surface region ofthe first seal ring segment, wherein the recess corresponds to thesidewall gas-venting structure.
 7. The method of claim 1: wherein thefirst IC die comprises a first semiconductor substrate, and a firstinterconnect structure over the first semiconductor substrate; whereinthe second IC die comprises a second semiconductor substrate, and asecond interconnect structure that separates the second semiconductorsubstrate from the first interconnect structure; and wherein the sealring structure separates the first interconnect structure from thesecond interconnect structure and perimetrically encloses the gasreservoir.
 8. The method according to claim 7, wherein the seal ringstructure is conductive but is electrically isolated from both the firstinterconnect structure and the second interconnect structure.
 9. Themethod according to claim 1, wherein at least one of the first seal ringsegment or second seal ring segment comprises a plurality of ring-shapedsegments that are concentrically aligned about a central axis which isperpendicular to the first face and the second face, and wherein thesidewall gas-venting structure includes an opening that passes fullythrough each of the plurality of ring-shaped segments.
 10. A method formanufacturing a three-dimensional (3D) integrated circuit (IC), themethod comprising: forming a first IC die precursor with a first sealring precursor extending outward from a face of the first IC dieprecursor, and wherein one or more conductive contact areas or plugs iscircumscribed by the first seal ring precursor, wherein the first sealring precursor includes a bonding surface region including a firstregion having a first width and a second region having a second widthless than the first width; performing a chemical mechanicalplanarization (CMP) process on the first seal ring precursor and the oneor more conductive contact areas or plugs, thereby forming a first ICdie having a first seal ring segment, wherein the CMP process makesupper surfaces of the one or more conductive contact areas or plugsco-planar with the first region of the bonding surface region andconcurrently recesses upper surfaces of the second region for the firstIC die; and bonding the first IC die to a second IC die so uppersurfaces of the one or more conductive contact areas or plugs of thefirst IC die directly contact one or more corresponding conductivecontact areas or plugs of the second IC die and wherein the uppersurface of the first regions of the first seal ring segment on the firstIC die directly contacts a second seal ring segment of the second IC dieand the recessed upper surfaces of the second region provide gas ventopenings to a gas reservoir between the first IC die and the second ICdie.
 11. The method of claim 10, further comprising: after bonding thefirst IC die to the second IC die, closing or covering the gas ventopenings to hermetically seal the gas reservoir from an ambientenvironment external to the 3D IC.
 12. The method according to claim 10,wherein the first seal ring segment comprises a series of cube-like orbox-like structures that alternate in height and width along a perimeterof the first seal ring segment so a pair of first cube-like or box-likestructures, which each have the first width and a first height, arearranged on opposite sides of a second cube-like or box-like structurehaving the second width and a second height, the first height beinggreater than the second height.
 13. The method according to claim 12,wherein the first cube-like or box-like structure has an uppermostsurface that is planar, and the second cube-like or box-like structurehas an uppermost surface that is rounded or tapered and which isrecessed below the uppermost surface of the first cube-like or box-likestructure. 14-20. (canceled).
 21. A method for manufacturing athree-dimensional (3D) integrated circuit (IC), the method comprising:forming a first seal ring segment over a first face of a first IC die,the first seal ring segment circumscribing a first contact area or plugon the first face; forming a second seal ring segment over a second faceof a second IC die, the second seal ring segment circumscribing a secondcontact area or plug on the second face, wherein at least one of thefirst seal ring segment and the second seal ring segment includes asidewall gas-venting structure; bonding the first seal ring segment tothe second seal ring segment so the first contact area or plug contactsthe second contact area or plug, thereby establishing a seal ringstructure that encloses a gas reservoir between the first face and thesecond face such that the sidewall gas-venting structure facilitates gasflow between the gas reservoir and an ambient environment surroundingthe 3D IC; and pinching off the sidewall gas-venting structure either byperforming a heat treatment to soften or liquefy material of the firstor second seal ring segment or by depositing a coating on an outersidewall of the seal ring structure.
 22. The method according to claim21, wherein the seal ring structure comprises a plurality of ring-shapedsegments that are concentrically aligned, and wherein the sidewallgas-vent structure includes an opening that passes fully through each ofthe plurality of ring-shaped segments.
 23. The method according to claim21, wherein the first seal ring segment includes a first sidewallgas-venting structure having a first opening that passes fully throughthe first seal ring segment and wherein the second seal ring segmentincludes a second sidewall gas-venting structure having a second openingthat passes fully through the second seal ring segment.
 24. The methodaccording to claim 23, wherein the first opening is aligned with thesecond opening so as to coalesce into a single opening passing fullythrough the first seal ring segment and fully through the second sealring segment.
 25. The method according to claim 1, wherein the firstseal ring segment includes a first sidewall gas-venting structure havinga first opening that passes fully through the first seal ring segmentand wherein the second seal ring segment includes a second sidewallgas-venting structure having a second opening that passes fully throughthe second seal ring segment.
 26. The method according to claim 25,wherein the first opening is aligned with the second opening so as tocoalesce into a single opening passing fully through the first seal ringsegment and fully through the second seal ring segment.
 27. The methodaccording to claim 10, wherein the first seal ring segment includes afirst sidewall gas-venting structure that passes fully through the firstseal ring segment and wherein the second seal ring segment includes asecond sidewall gas-venting structure that passes fully through thesecond seal ring segment.